To address these challenges, some existing methods [1]}, [2]}, [3]}, [4]}, [5]}, [6]} adopt axis-aligned rectangles, rotated rectangles or quadrangles to localize scene texts. Despite their progress on horizontal or multi-oriented texts, these methods may fall short, when handling arbitrary-shape texts that are ubiquitous in the real life, as shown in Figure REF  (a)(b)(c).To accurately localize arbitrary-shape text contours in the natural image (Figure REF  (d)), two kinds of methods are prevalent in the field of scene text detection. One is top-down based methods. They perform the binary segmentation or the regression of arbitrary-shape text contour points on the proposals.The other is bottom-up based methods.They first predict local units (, pixels, connected components) and their auxiliary information, and then group them into different text instances.
